They are the construction workers and engineers of Earth orbit. In the vacuum and zero gravity of outer space, where temperatures can range from -150 degrees C to 120 degrees C in a matter of minutes, they have rescued the crippled Hubble Space Telescope; repaired the Space Shuttle and built the International Space Station. Spacewalkers are an elite within an elite. Not every astronaut has left the relative safety of a spacecraft to replace a faulty component or free a jammed bolt, protected from space by just a spacesuit. It’s hard work: a simple task like changing an electrical connector that would take minutes on Earth can take hours in space. And that’s hours – the record stands at nine hours for a single spacewalk – without food or a bathroom. In space, you can’t even blow your nose.